1. Field of the Invention
The present invention relates to the repair of combustion turbines. More specifically, the invention provides a jig for guiding a grinder and resizing of portions of a turbine casing that have been repaired by welding.
2. Description of the Related Art
The vanes, or non-rotating blades, within a combustion turbine are typically secured to either the cover or base of the turbine by rings known as blade diaphrams. These rings and the corresponding non-rotating blades sit into channels defined within the casing, with the channels defining hook fits along their sides to secure the blade diaphragms and corresponding non-rotating blades in place.
Combustion turbines are subjected to a harsh operating environment, given both the temperature and the pressure of the gas flowing therethrough. It is therefore occasionally necessary to perform repairs to the hook fits of the combustion turbine by welding various portions of the casing.
Each section of the base and the cover of the casing corresponding to each row of blades and/or veins has a different diameter. Therefore, after welding is performed, grinding down the wells to restore the dimensions of that portion of the casing is difficult. In the past, hand grinding was used, but this is very time consuming, and is also a very difficult process with which to obtain the proper dimensions within the desired tolerance.
While the cover of the casing may be grinded using a grinder guided by a boring bar mounted substantially along its longitudinal axis, the use of a boring bar on the base would require removal of the rotor, which would add approximately six weeks to the time required to complete the repair.
Accordingly, there is a need for a jig that is structured to guide a grinder along a weldment within the base or cover of the combustion turbine, so that the proper dimensions and tolerances may be quickly achieved during grinding. Such a jig would not only cut down on the time required for repair, but would also increase the accuracy with which the desired dimensions may be achieved in the repaired casing.